Vol 79, No 5 (2024)

An overview of the main applications of generalized two-dimensional correlation spectroscopy (2D-COS) in analytical chemistry is presented. 2D-COS is a method used to analyze datasets obtained from spectroscopic measurements. This approach is based on the use of two-dimensional correlation maps to identify and analyze correlations between different regions of the spectrum or data from two measurement methods. The purpose of using 2D-COS is to increase the amount of analytical information by revealing hidden data correlations. Analyzing such correlations for series of spectral data obtained for a certain range of analyte concentrations, pH, or component ratios of a mixture, as well as changes in temperature or other external factors, allows researchers to investigate and identify chemical processes and interactions that cannot be directly obtained from the spectra. Compared to one-dimensional spectra, 2D-COS offers significant analytical information for complex mixtures, particularly in identifying components and determining composition. Additionally, 2D-COS can be used to monitor changes in a sample over time, making it a valuable tool for studying dynamically changing systems. Overall, 2D-COS is a highly versatile approach that can be used in conjunction with a large number of methods for most analytical tasks and complex objects, including those without sample preparation. The review presents advancements in the application of 2D-COS as of early September 2023.

Aquatic ecosystems are the primary reservoir for microplastics entering the environment. Assessing the content of microplastics in natural waters and sediments is a critical task necessary for evaluating the pollution levels of water bodies, identifying sources of pollution, and assessing potential risks to aquatic life. To date, there is no universal analytical approach for extracting microplastics from natural waters and sediments for subsequent identification. This review summarizes information on methods of microplastic sampling from natural waters and sediments and methods of sample preparation, including techniques for separating particles by size and density, as well as methods based on the chemical decomposition of samples to remove natural organic matter. Additionally, the classification of microplastics, as well as general information about the content of microplastics in aquatic ecosystems and their potential toxicity, are described.

A method for synthesizing new supramolecular structures consisting of silver nanoparticles (NPs) whose surfaces are covered with spontaneously formed ordered micelle-like aggregates of cetyltrimethylammonium bromide (CTAB) molecules is proposed. The study of the self-assembly processes of CTAB molecules on the surface of silver nanoparticles and the structure of the resulting associates was carried out using the fluorescence probe method (molecular probe – pyrene). Optimal conditions for obtaining new supramolecular structures were determined. The proposed supramolecular structures can be used for the luminescent determination of various chemical compounds. The formation of the analytical signal in this case will be determined by the interaction of the analyte with micelle-like aggregates located near the silver nanoparticles and will depend on both the structure of the aggregate and the polarity of the analyte.

The patterns of concentrating Cu(II) and Zn(II) ions from aqueous solutions with N-nonanoyl-N’-mesylhydrazine by the ion flotation method were studied, depending on the initial concentration of the collagents, the pH value of the solution, conditioning time, and temperature. Based on IR spectroscopy and elemental analysis data, a hypothesis about the composition of the floated compounds was made. It was shown that the extraction of Zn(II) is significantly dependent on the initial concentration of the metal and the conditioning time of the solution. A decrease in the extraction degree of the studied ions with an increase in the solution temperature was established, with this effect being more pronounced for Cu(II). The kinetics of the process were described using the classical first-order model; the obtained flotation rate constants for Zn(II) ions were five times higher than for Cu(II). The conditions for the selective separation of Cu(II) ions in collective flotation conditions were determined.

The concentration of strontium and barium in the form of complexes with 11 organic reagents by co-precipitation with organic co-precipitants was studied for their subsequent determination by the X-ray fluorescence method. The most effective systems were those including reagents from the group of bisazo-substituted chromotropic acids—Nithchromazo and Chlorophosphonazo III. The complexes of these metals were almost quantitatively co-precipitated in the form of associates with the cations of the Brilliant Green dye when the collector was an associate of an excess of the analytical reagent with the cations of this dye. It was shown that the additional use of polyvinyl butyral as an indifferent co-precipitant allows not only the almost complete extraction of these elements from solutions but also the preparation of emitter concentrates suitable for X-ray fluorescence measurements using the background standard technique. The high efficiency allows reaching very low detection limits (IUPAC): 0.03 µg/mL for Sr and 0.19 µg/mL for Ba, even when working with small-volume samples.

The method of atomic emission spectrometry with excitation spectra in microwave plasma was used to determine the composition of lanthanum sulfide crystals and europium-doped gadolinium oxide, as well as elements in the melt (tin, boron, and lithium). Calibration curves for rare earth elements are nonlinear and do not provide the required accuracy of analysis. To reduce errors and linearize the calibration curves, the internal standard method was used. Molecular ions N2, N2+ and OH did not correct for changes in plasma conditions and inter-element effects. Internal standard elements were selected based on the proximity of the first ionization potential to the analytes, considering Ba, Al, Ga, and In. The use of these elements as internal standards allowed the linearization of calibration curves, achieving an analytical accuracy of 95−105%. The found total mass of the elements was 97−103% of the sample mass, with accuracy confirmed by the method of standard additions.